Lakeshore 325, Руководство пользователя, Страница: 84 / 166

Lake Shore Model 325 Temperature Controller User’s Manual
5-8 Advanced Operation
5.3.3
SoftCal™ with Platinum Sensors
The platinum sensor is a well-accepted temperature standard because of its consistent and repeatable temperature
response above 30 K. SoftCal gives platinum sensors better accuracy than their nominal matching to the DIN 43760
curve.
C-325-5-2.bmp
Figure 5-2. SoftCal Temperature Ranges for Platinum Sensors
One, two, or three calibration data points can be used. If using one point, the algorithm shifts the entire curve up or down
to meet the single point. If using two points, the algorithm has enough information to tilt the curve, achieving good
accuracy between the data points. The third point extends the improved accuracy to span all three points.
Point 1: Calibration data point at or near the boiling point of nitrogen (77.35 K). Temperatures outside 50 K to 100 K are
not allowed.
Point 2: Calibration data point near room temperature (305 K). Temperatures outside 200 K to 350 K are not allowed.
Point 3: Calibration data point at a higher temperature (480 K). Temperatures outside 400 K to 600 K are not allowed.
5.3.4
SoftCal™ Accuracy with Platinum Sensors
A SoftCal calibration is only as good as the accuracy of the calibration points. The accuracies listed for SoftCal assume
±0.05 K for 77.35 K (liquid nitrogen) and 305 K (room temperature) points. Users performing the SoftCal with Lake
Shore instruments should note that the boiling point of liquid cryogen, though accurate, is affected by atmospheric
pressure. Use calibrated standard sensors if possible.
One-point SoftCal calibrations with platinum sensors have no specified accuracy.
Two-point SoftCal calibrations for applications above 70 K are performed at liquid nitrogen (77.35 K) and room
temperature (305 K). Accuracy for the PT-102, PT-103, or PT-111 platinum sensor is as follows:
±250 mK from 70 K to 325 K

±500 mK from 325 K to

±1400 mK at 480 K
(DIN Class A or Class B tolerance)
Three-point SoftCal calibrations are performed at liquid nitrogen (77.35 K), room temperature (305 K), and high
temperature (480 K). Accuracy for the PT-102, PT-103, or PT-111 platinum sensor is
±250 mK from 70 K to 325 K, and
±250 mK from 325 K to 480 K.